Ablation of myocardial tissue is well known as a treatment for cardiac arrhythmias. In radio-frequency (RF) ablation, for example a catheter is inserted into the heart and brought into contact with tissue at a target location. RF energy is then applied through electrodes on the catheter in order to create a lesion for the purpose of breaking arrhythmogenic current paths in the tissue.
Ablation has been accomplished primarily by means of focal ablation, that is, ablation by a tip electrode at a distal end of the catheter. Thus, for linear ablation along a line or curve, the tip electrode is repositioned repeatedly or dragged across the tissue along the line or curve during a prolonged ablation.
Also known are irrigated ablation tip and ring electrodes which are effective at reducing electrode temperature during ablation to minimize the formation of char and coagulum. However, fluid load on the patient is a concern, especially where multiple electrodes are being irrigated.
Current EP catheters utilize a single irrigation lumen to deliver irrigation to one or more irrigated electrodes. Pump units consisting of one pump head are therefore used. As catheters become more complex, the need for multiple irrigation lumens becomes more critical. Currently, irrigation delivery to a catheter with multiple irrigation lumens requires the use of multiple pump units.
Accordingly, there is a desire for a catheter adapted for both focal and linear ablation so that a linear lesion can be formed without repositioning of the catheter. In particular, there is a desire for a catheter with tip and ring electrodes adapted for uni-polar and bi-polar ablation. Such a catheter would advantageously reduce procedure time and improve clinical efficacy of such procedures. And where such tip and ring electrodes are irrigated, there is also a desire that the fluid flow through these electrodes be controlled and variable, if not also dependent on the selective energization of the irrigated electrodes. To that end, there is a further desire for an integrated ablation system that includes an irrigation pump adapted to supply fluid in multiple independent flow paths so that selected electrodes or sets of electrodes can receive fluid at different flow rates, especially where the flow rates are dependent on the energization state of the electrodes.